1. Field of the Invention
The present invention relates generally to a broadband optical source. More specifically, it relates to a broadband optical source with a flat spectral output and high output power for use in a fiber optic sensor interface system.
2. Description of the Related Art
Fiber optic sensor interface systems are currently being developed in order to replace corresponding electrical systems used to measure and control the positions of flaps and slats at various locations throughout an aircraft. One approach to replacing an electrical sensor interface system with a fiber optic interface system involves using a broadband optical source which launches optical signals down a plurality of fiber optic paths as discussed, for example, in U.S. Pat. No. 4,842,357, incorporated herein by reference. These optical signals illuminate various reflective surfaces of different sensors corresponding to the flaps and slats. The resulting wavelength encoded reflected signals from the various sensors are de-multiplexed using a glass slab grating (a so-called wavelength de-multiplexing or WDM grating) into a detector array. The detector array is integrated into processing electronics on board the aircraft. The processing electronics determine and control the positions of the flaps and slats using the data output by the detector array. The various sensors used in the fiber optic sensor interface system may not necessarily use optical radiation with the same wavelengths. For example, a first sensor may require radiation with center frequencies .lambda.11, .lambda.12, .lambda.13 whereas a second sensor may require radiation with center frequencies at .lambda.21, .lambda.22, .lambda.23. Such a "univeral" fiber optic sensor interface system then requires six individual light sources, one for each of the required wavelengths, .lambda.11, .lambda.12, .lambda.13, .lambda.21, .lambda.22, .lambda.23. Therefore, it is desireable to use a single optical source capable of outputting appropriate power over a wide spectrum of wavelengths. Such an optical source would preferably have a flat (e.g. .ltoreq. 3dB variation), broadband (spanning e.g. from 0.75 .mu.m to 0.9 .mu.m) spectrum and should be capable of relatively high (e.g. .gtoreq.]500 .mu.w) output power levels. Particular requirements are determined by the fiber optic sensor interface system requirements. The desired flatness, for example, is determined by the dynamic range of the fiber optic sensor interface system.